1. Field of the Invention
The present invention relates to a liquid ejection head that performs printing by ejecting liquid onto a print medium.
2. Description of the Related Art
In recent years ink jet methods are being abundantly adopted in printing apparatus as one of the predominant printing methods. The capability of performing printing without the print head, in the form of a liquid ejection head, contacting the sheet or other print medium, the ease of changing colors, and high quietness are raised as some of the advantages of ink jet methods. Nevertheless, generally, in ink jet printing apparatus based on ink jet printing methods, as the surrounding temperature becomes lower the viscosity of the ink used in printing increases. For this reason, in the case where an ink jet printing apparatus is in an extremely low temperature environment, phenomenon such as the decrease of the volume of the ink ejected from the print head (ejection volume fluctuation), and the non-performance of normal ink ejection (improper ejection) arise. In this case, accompanying the fluctuation in ejection volume, undesirable dot formation and the like, due to density unevenness or improper ejection, can often be seen in the image obtained from printing. In this case there is a possibility that print quality is degraded. In order to eliminate occurrences of such ejection volume fluctuations and improper ejections, heating control is performed in traditional ink jet printing apparatus before the printing operation or during the printing operation such that the print head temperature falls within a prescribed range. As one method of achieving this, heat generation elements (hereinafter called “preliminary heating heaters” or “sub-heaters”) are provided in the print head, for heating the ink jet print head. Hence, under low temperature environments the temperature of the ink jet print head and the ink inside the ink jet print head is regulated by driving of the sub-heaters. Regulation of ink jet print head temperature makes it possible to stabilize the volume of ink ejected from the ink jet print head, in this manner.
One example of an ink jet printing apparatus with a sub-heater, serving as a preliminary heater used to control the temperature of the print head, is disclosed in Japanese Patent Laid-Open No. 2006-224444. According to the ink jet printing apparatus disclosed in Japanese Patent Laid-Open No. 2006-224444, in an ink jet print head having at least two nozzle arrays with different ink ejection volumes, a temperature regulation sub-heater is arranged near the nozzle array with the smaller ink ejection volume. From this, it is possible to more responsively control the temperature of the nozzle array with the smaller ejection volume and it's its vicinity, and moreover, without particularly increasing the number of sub-heaters, it is possible to avoid the considerable fluctuation of ink ejection volume caused by increases in ink viscosity and the like.
However, in the case where sub-heaters disclosed in Japanese Patent Laid-Open No. 2006-224444 are deployed in a print head, the sub-heater is arranged at a position separated from the ink supply port on the substrate. Consequently the quantity of heat added to the ink stored inside the ink supply port may be insufficient. Improper ejection may occur as a result due to the commencement of printing with the ink temperature remaining low and ejecting ink with the viscosity remaining high. Furthermore, the case of carrying out heating for a longer time in order to sufficiently increase ink temperature may cause an increase in the total printing time.